21651404 has 12 divisors (see below), whose sum is σ = 40118904. Its totient is φ = 10188864.

The previous prime is 21651391. The next prime is 21651419. The reversal of 21651404 is 40415612.

It is a self number, because there is not a number n which added to its sum of digits gives 21651404.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 159134 + ... + 159269.

It is an arithmetic number, because the mean of its divisors is an integer number (3343242).

Almost surely, 2^21651404 is an apocalyptic number.

It is an amenable number.

21651404 is a deficient number, since it is larger than the sum of its proper divisors (18467500).

21651404 is a wasteful number, since it uses less digits than its factorization.

21651404 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 318424 (or 318422 counting only the distinct ones).

The product of its (nonzero) digits is 960, while the sum is 23.

The square root of 21651404 is about 4653.1069190381. The cubic root of 21651404 is about 278.7160774340.

The spelling of 21651404 in words is "twenty-one million, six hundred fifty-one thousand, four hundred four".